Keysight Technologies E8257D Service Manual page 88

Troubleshooting
Troubleshooting Assembly–Level Problems
4. If self–test Quad Loop Integrator fails, replace the A35 I/Q Modulator.
1207 Upconverter
1. If the power supplies +6.5V or +5.2V fail, refer to the table
2. If any of the drain currents fail (test indexes 3 through 18), replace the A37
3. If self–tests ALC (indexes 18 through 32) Vdet (indexes 24 through 26) fail:
88
4. Execute a single 1206 self–test. The signal on the
check the supplies used by the A37 Upconverter as they leave the A26
MID connector.
— If the signals are good at the A26 MID connector, replace the A37
Upconverter.
Upconverter.
a. On the signal generator, set the following:
Center Frequency: Value at which ACL or Vdet self–test failed (e.g.
20.01 GHz, 28.5 GHz, etc.)
Power: +20 dBm
RF: On
b. Disconnect A35–J24 and connect a spectrum analyzer to the A35
I/Q Modulator. This is the IF signal to the A37 Upconverter.
c. For RF signals >20 GHz to 28.5 GHz, the IF signal is mixed with the
LO to produce the downconverted RF signal. The IF signal will range
in frequency from 6.667 GHz to 9.50 GHz with an amplitude of
>5 dBm.
— If the signal is bad, troubleshoot the A35 RF path.
— If the signal is good, reconnect A35–J24.
d. On the A37 Upconverter, disconnect J5 and connect a spectrum
analyzer to the cable coming from the A27 40 GHz Doubler. This is
the LO signal to the A37 Upconverter.
e. For RF signals >20 GHz to 28.5 GHz, the IF signal is mixed with the
LO to produce the downconverted RF signal. The LO signal will
range in frequency from 26.667 GHz to 38 GHz and will be four
times the IF frequency. The amplitude of the LO signal should be
>5 dBm.
— If the signal is bad, troubleshoot the A35 RF path.
E8257D/67D, E8663D PSG Signal Generators Service Guide
oscilloscope should pulse to approximately
18 millivolts for approximately 500 ms.
— If the signal is bad, refer to the A13 I/Q
Multiplexer troubleshooting.
— If both the I and Q signals are good,
replace the A35 I/Q Modulator.
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